INSIVUMEH and CONRED reported that during 29-30 May lahars descended Santa María's San Isidro drainage (tributary of El Tambor), carrying blocks 1-3 m in diameter and tree trunks. The lahars were 20 m wide and 1.5 m deep; CONRED noted that the 29 May lahar was hot and had a sulfur odor. Explosions recorded during 30 May-4 June generated ash plumes that rose as high as 800 m above the crater and drifted E and SE. Avalanches of material descended the E and SE flanks.

Geological Summary. Symmetrical, forest-covered Santa María volcano is part of a chain of large stratovolcanoes that rise above the Pacific coastal plain of Guatemala. The sharp-topped, conical profile is cut on the SW flank by a 1.5-km-wide crater. The oval-shaped crater extends from just below the summit to the lower flank, and was formed during a catastrophic eruption in 1902. The renowned Plinian eruption of 1902 that devastated much of SW Guatemala followed a long repose period after construction of the large basaltic-andesite stratovolcano. The massive dacitic Santiaguito lava-dome complex has been growing at the base of the 1902 crater since 1922. Compound dome growth at Santiaguito has occurred episodically from four vents, with activity progressing E towards the most recent, Caliente. Dome growth has been accompanied by almost continuous minor explosions, with periodic lava extrusion, larger explosions, pyroclastic flows, and lahars.

Sources: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH), Coordinadora Nacional para la Reducción de Desastres (CONRED)